1. Field of the Invention
This invention relates to an apparatus and method for measuring the relative volumes of the various phases present in a multiphase stream, and, more particularly, to an improved apparatus and method capable of quickly and reliably determining the relative amounts of the various phases found in a multiphase stream, such as a stream of petroleum produced from an oil and gas well.
2. Description of the Related Art
It is often important to have a quick and reliable quantitative indication of the relative amounts of the various phases present in a stream containing multiple phases. Such streams are often encountered in a refinery or chemical plant. Without in any way limiting the application of the present invention, it is suggested that application of the present invention is of special benefit in the context of the production of petroleum from oil and gas wells.
Produced petroleum streams typically contain multiple phases. Prior to its production to the surface, petroleum in the reservoir contains varying amounts of dissolved gas. This gas separates from the liquid when the petroleum is brought to the surface and the pressure is released. A significant fraction of production wells, in addition, produce varying amounts of water at certain stages during their production lives. Thus, the typical oil well produces a stream which is made up of two or even three phases.
Without unduly elaborating on well known reservoir engineering principles, it is generally accepted that knowledge of the relative amounts of the various fluid phases, often expressed as the gas-oil-ratio (GOR) or water-oil-ratio (WOR), is often crucial to understanding a well. This knowledge is also one of the keys to decisions intended to optimize the commercial value of the well and reservoir from which the well is producing.
Knowledge of the relative amounts of the various phases can be obtained by observing the amount of water, oil and gas phases in a holding tank into which the production of the well is routed for storage. However, in typical operations, a number of nearby wells may be routed to the same tank, making it unfeasible to determine the relative amounts of the phases of the individual wells. Often also, well production from surrounding wells is piped directly into a field plant which again makes it unfeasible to gauge the performance of an individual well.
There has long been a need for an instrument or apparatus which could be installed in the field on or near the site of an operating well which would be able to periodically measure the relative amounts of the various fluid phases present.